Hydraulic track tensioning means



Aug. 27, 1963 J- H. HYLER ETAL 3,101,977

HYDRAULIC TRACK TENSIONING MEANS Original Filed March 7, 1958 PRESSUREZ61 ACCUMULATOR ZSO --2b'5 23 ZIZ 45: 2.57 ill I Z42 FIG.2 7

11 so! so? .3 5 3 INVENTORS. q 7 2.15 JOHN H. HYLER I I ERNST W.SPANNHAKE 3,ll,977 Patented Aug. 27, 1963 3,101,977 HYDRAULIC TRACKTENSIONENG MEANS John H. Hyler, Peoria, Ill., and Ernst W. Spannhalrc,Butler, N.J., assignors to LeTourneau-Westinghouse pompany, Peoria,111., a corporation of Illinois Ongma] application Mar. 7, 1958, Ser.No. 719,838, new Patent No. 2,998,998, dated Sept. 5, 1961. Divided andthis application Oct. 25, 1960, Ser. No. 64,926

7 Claims. (Cl. 305-10) This invention relates to a land vehicle, andmore especially, to a land vehicle of a type which is adapted to move onpneumatic tires or on a track mounted on the pneumatic tires, at theoption of the operator. This application is a division of applicationSer. No. 719,838, filed March 7, 1958, now Patent 2,998,998, issuedSeptember 5, 1961, and assigned to the assignee of this invention.

There are many places in the construction and earthmoving industry whichcall for track-laying vehicles capable of negotiating all types ofterrain. Such vehicles may have to pass through soft mud one minute anda dry rock-strewn area in the next minute. Such a vehicle must becapable of producing suflicient traction under all of the variedcircumstances, and it must moreover be capable of keeping its track ortracks on in spite of rocks, tree branches, or the like which may comebetween the track and the tires. If the track should happen to breakbecause of the extremely rough usage, it is desirable that the operatorbe able to take the vehicle back to a repair point under its own power,or even to operate the vehicle under certain conditions without tracks.

It is accordingly an object of this invention to provide a land vehiclewhich under many operating conditions operates as a track-layingvehicle, the track of the vehicle being under very high tension,controlled or regulated according to the weight of the vehicle, so thatthe track itself can carry the vehicle load even though the contactpoints under the wheels often do not touch the ground. It is anotherobject of this invention to provide a vehicle which can operatetrack-laying or wheeled. Other objects will become apparent to thoseskilled in the art from a study of the following description and theaccompanying drawings.

In the drawings:

FIG. 1 is a diagrammatic or schematic side elevation view illustrating avehicle embodying the invention; and

FIG. 2 is a view in section showing details of a valve used in theembodiment of FIG. 1.

Referring now in detail to the drawings, in FIG. 1 we have shownschematically an embodiment of the invention. In that figure, a sideelevation view of the wheels and a simplified track are shown. Morespecifically, wheels 242 and 244 are shown on axles 21?. and 230respectively, and equipped with pneumatic tires 246 and 24-8.

Axle 230 is mounted for limited movement relative to axle 212, and thismounting may be by any suitable means which need not be detailed here. Aflexible band track 250 tightly engages the tires 246 and 248 and iskept tight by means which bias the axles apart in accordance with thevehicle load. As here shown, these means consist of a hydraulic jack 251connected to the axles and kept under suitable pressure.

More specifically, jack 251 consists of a cylinder member 253 and apiston member 255 reciprocable therein and connected with a piston rod257. Cylinder member 253 is connected by any suitable means 259 withaxle 230, and piston rod 257 is suitably connected with axle 212. Asshown, the jack 251 is of the single-acting type, being vented on theatmospheric pressure side of the piston as shown at 261. The other endof the cylinder is connected with one end of a conduit 263. Conduit 263connects at its other end with a T 265 which in turn taps into theliquid chamber of an olcopneumatic pressure device of the general typeshown in Reissue Patent 23,437 and here shown at 267. The other branchof the T connects with a conduit 269 which in turn is connected with avalve 271.

By means of a conduit 275, valve 271 is supplied with fluid underpressure from a suitable source 273 which includes a reservoir 277. Asuitable conduit 279 is connected to return liquid from valve 271 to thereservoir.

Valve 271 is shown in detail in FIG. 2. As there shown, a body member281 is provided with a substantially central bore 283 in which a valvespool 285 is slidably disposed.

The valve body 281 is provided with annular grooves communicating withthe central bore and with conduits 275 and 279. As shown, an annulargroove 287 communieatcs with conduit 275 and a similar annular groove289 communicates with conduit 279. A suitable projection 291 is providedat one end of the bore for the accurate location of spool 285 at onelimit of its travel.

Spool 285 is provided with a central bore 293 running from the extremeleft end of the spool to a cross bore 295 which is spaced from the rightend of the spool. Another cross bore 297 communicates with the centralbore and is disposed between the left end of the spool and the bore 295.The spacing of the cross bores 295 and 297 is related to annular grooves287 and 289 in such a way that, with the valve spool at the leftwardlimit of its travel, the ends of cross bore 295 are partially uncoveredby annular groove 287 and movement of spool 285 to the right graduallyshuts off the communication of cross bore 295 with annular groove 287.Cross bore 297, in the extreme leftward position of spool 285, isblocked by the surface of bore 283 in valve body 281. However, aftervalve spool 285 has moved to the right sufficiently to block the ends ofcross bore 295, the ends of cross bore 297 are uncovered by the annulargroove 289. It will of course be appreciated by those skilled in the artthat the ends of cross bore 295 will be closed before the ends of crossbore 297 are uncovered. Valve body 281 is provided at its right end witha closure 299 which may be secured to the valve body in any suitablemanner as for example by the threaded means 301. The closure member 299has a substantially central threaded opening adapted to re ceive asimilarly threaded screw 303. At its outer end, screw 303 has secured toit a suitable hand wheel 365. The other end of screw 303 engages aspring seat 307. A spring 309 is compressed between spring seat 307 andthe right end of valve spool 285.

As is best seen in FIG. 1, this form of the invention in its preferredembodiment is arranged to provide a pointer 511 on the hand wheel 395.Pointer 311 cooperates with a suitably calibrated scale 313. As will beunderstood by those skilled in the art, scale 313 will be mounted so asto be stationary relative to the valve body 281. It wi l also be evidentfrom the foregoing that pointer 311 and scale 313 together constitute anindicator.

The scale 3E3 may be calibrated in any units desired. In a preferredform of the invention, the scale could be calibrated in terms of vehicleload.

Operation Track 259 operates under a very high tension, such that if thevehicle runs over a log or other projection engaged by the track midwaybetween wheels 242 and 244, notwithstanding any appreciable deflectionof track 250 that may occur, the track itself supports the weight of thevehicle without those portions of the track under the wheels being incontact with the ground.

Notwithstanding the high tension in the track, the combination of trackand tires is nevertheless sufficiently yielding to permit foreignobjects such as sizable branches, rocks, and the like, to find their waybetween the track and the pneumatic tires and to work their way aroundwithout throwing the track off the wheels.

Moreover, the tension in the track is great enough to drive the track inevery kind of terrain, even in mud, because the tension is such that mudwhich would be soft enough to make the track slippery is simply squeezedout, while mud of a heavier consistency at first packs under the tiresbut can then be stripped off by suitable battles (not shown) and thrownto one side.

If for some reason the track should break, the vehicle can be operatedon its rubber tires, in which case the jack 251 is extended, either allthe way or until the system comes against a suitable stop (not shown).

The system will be charged with fluid under pressure in a manner whichwill be well understood by those skilled in the art and which need notbe detailed here. If, in order to compensate for a heavier vehicle load,a higher track tension is desired, the operator turns the hand wheel 305until the pointer indicates the load, or such other unit in terms ofwhich the scale 313 is calibrated. Assuming that the threaded member 303is provided with a right hand thread, turning the hand wheel 305clockwise as seen from the right end of FIG. 2 will tighten up orincrease the compression of spring 309. The increased pressure willforce valve spool 285 leftward to register the ends of cross bore 295with the annular groove 287. Fluid under pressure will then becommunicated from the fluid pressure source 273 to the accumulator 267and the cylinder 253 by way of conduit 275, annular groove 287, crossbore 295, central bore 293, conduit 269, T 265 and conduit 263. Theincrease in pressure will compress the air in accumulator 267sufficiently to establish the higher pressure in the accumulator. Thehigher pressure is of course also transmitted to cylinder 253 and servesto bias the axles 212 and 230 apart with a greater force than waspresent before hand wheel 305 was turned. Even though there may be noappreciable separation of axles 212 and 230, the force tending to pushthem apart will be increased and this will increase the tension on theband track 250. With the increasing tension, the band track will againbe able to operate to secure the advantages set forth above in thediscussion of the desirability of maintaining the track tension at ahigh level.

As the vehicle rolls over the terrain, the track is maintained undertension by a substantially constant force, by means of jack 251 and itsconnection with accumulator 267. As is well understood by those skilledin the art, any amount of fluid displacement in a finite accumulatorwill result in variations in fluid pressure in the system and thus invariations in the track tension. However, by selecting an accumulatorwhich has a large capacity relative to the rest of the hydraulic system,a vehicle can be designed in which even a large variety of terrainconditions can be negotiated without reducing the track tension enoughto induce slipping of the wheels in the track or increasing tensionenough to put intolerable loads on bearings, track, tires, etc. Withinthe limits of such considerations, track tension would be maintained bya substamtially constant force.

If now the load on the vehicle is lightened, and the operator desires todiminish track tension in order to reduce the wear on bearings, on thetrack itself, and the like, the operator turns the hand wheel 305counter-clockwise by the indicated amount, thus reducing the compressiveforces on spring 309. This unbalance in the system and the pressure inconduits 263 and 269 is suflicient to shift valve spool 285 to the rightuntil cross bore 297 registers with annular groove 289. Some liquidunder pressure is thereupon bled out of the system through the valve byway of central bore 293, cross bore 297, and waste conduit 279, to thereservoir 277. Liquid bleeds out until the system is again substantiallyin balance, whereupon the mechanism is in a new state of equilibrium inaccordance with the new load. Once again the accumulator 267 serves tomaintain the system under a substantially constant pressure which issomewhat lower than the pressure in the system before hand wheel 305 wasturned counter-clockwise.

It will be clear from the foregoing that the illustrated inventionprovides a land vehicle of a track-laying type which may operate in alltypes of terrain and which may if necessary be operated trackless. Itwill also be evident from the foregoing that, in the hydraulic systemhere disclosed and claimed, accumulator 267 is at all times responsiveto normal operating pressures and pressure variations in jack 251i.e.,as long as jack 251 is a factor in maintaining track tension,accumulator 267 responds to whatever pressure obtains in jack 251. Otheradvantages will be apparent to those skilled in the art.

While this application shows one form which the invention may take inpractice, it will be understood that this form is shown for purposes ofillustration and that the invention may be modified and embodied invarious other forms without departing from its spirit or from the scopeof the appended claims.

What is claimed is:

l. A track laying vehicle comprising: wheels; resilient tires on thewheels; at least one flexible band track tightly engaging at least twowheels; fluid pressure operated means to maintain tension in the track;a source of fluid under pressure; a conduit having a connection with thesource; a second conduit for the discharge of spent fluid; a thirdconduit connected with the fluid pressure operated means; a fluidpressure responsive fluid conducting element having passages and anoperating position in which the passages connect the first and thirdconduits and a second operating position in which the passages connectthe first and third conduits and a second operating position in whichthe passages connect the second and third conduits; means biasing saidelement against fluid pressure into one of said positions and resistingmovement from that position to the remaining one of said positions; andmeans to vary the resistance of said biasing means.

2. A track laying vehicle comprising: wheels; resilient tires on thewheels; at least one flexible band track tightly engaging at least twowheels; fluid pressure operated means to maintain tension in the track;a source of fluid under pressure; a conduit having a connection with thesource; a second conduit for the discharge of spent fluid; a thirdconduit connected with the fluid pressure operated means; a fluidpressure responsive fluid conducting element having passages and anoperating position in which the passages connect the first and thirdconduits and a second operating position in which the passages connectthe second and third conduits; means biasing said element against fluidpressure into the first-named one of said positions and resistingmovement from that position to the secondnamed position; and means tovary the resistance of said biasing means.

3. A track laying vehicle comprising: wheels; resilient tires on thewheels; at least one flexible band track tightly engaging at least twowheels; fluid pressure operated means to maintain tension in the track;a source of fluid under pressure; a conduit having a connection with thesource; a second conduit for the discharge of spent fluid; a thirdconduit connected with the fluid pressure operated means; a fluidpressure responsive fluid conducting element having passages and anoperating position in which the passages connect the first and thirdconduits and a second operating position in which the passages conmeetthe second and third conduits; means biasing said element against fluidpressure into one of said positions and resisting movement from thatposition to the remaining one of said positions; and operator-operablemeans, including an indicator calibrated in terms of vehicle load,

to vary the resistance of said biasing means in accordance with vehicleload.

4. A track laying vehicle comprising: wheeis; resilient tires on thewheels; at least one flexible band track tightly engaging at least twowheels; fluid pressure operated means to maintain tension in the track;a source of fluid under pressure; a conduit having a connection with thesource; a second conduit for the discharge of spent fluid; a thirdconduit connected with the fluid pressure operated means; a fluidpressure responsive fluid conducting element having passages and anoperating position in which the passages connect the first and thirdconduits and a second operating position in which the passages connectthe second and third conduits; preloaded elastically deformable meansbiasing said clement against fluid pressure into one of said positionsand resisting movement from that position to the remaining one of saidpositions; and means to vary the resistance of said biasing means.

5. A track laying vehicle comprising: Wheels; resilient tires on theWheels; at least one flexible band track tightly engaging at least twowheels; fluid pressure operated means to maintain tension in the track;a source of fluid under pressure; a conduit having a connection with thesource; a second conduit for the discharge of spent fluid; a thirdconduit connected with the fluid pressure operated means; a fluidpressure responsive fluid conducting element having passages and anoperating position in which the passages connect the first and thirdconduits and a second operating position in which the passages connectthe second and third conduits; preloaded elastically deformable meansbiasing said element against fluid pressure into one of said positionsand resisting movement from that position to the remaining one of saidpositions; and operator operable means, including an indicatorcalibrated in terms of vehicle load, to vary the resistance of saidbiasing means in accordance with vehicle load.

6. A track laying vehicle comprising: wheels; resilient tires on thewheels; at least one flexible band track tightly engaging at least twowheels; fluid pressure operated means to maintain tension in the track;a source of fluid under pressure; a conduit having a connection with thesource; a second conduit for the discharge of spent fluid; a thirdconduit connected with the fluid pressure operated means; a fluidpressure responsive fluid conducting element having passages and anoperating position in which the passages connect the first and thirdconduits and a second operating position in which the passages connectthe second and third conduits; preloaded elastically deformable meansbiasing said element against fluid pressure into one of said positionsand resisting movement from that position to the remaining one of saidpositions; and means, including an indicator calibrated in terms ofvehicle load, to vary the amount that the deformable means is preloaded.

7. A track laying vehicle comprising: wheels; resilient tires on thewheels; at least one flexible band track tightly engaging at least twowheels; fluid pressure operated means to maintain tension in the track;an accumulator connected to the fluid pressure operated means andresponsive to all normal operating pressure variations therein; a sourceof fluid under pressure; a reservoir connected with the source; aconduit having a connection with the source; a second conduit connectedwith the reservoir; a third conduit connected with the accumulator andthe fluid pressure operated means; a fluid pressure responsive fluidconducting element having passages and an operating position in whichthe passages connect the first and third conduits and a second operatingposition in which the passages connect the second and third conduits;means biasing said clement against fluid pressure into one of saidpositions and resisting movement from that position to the remaining oneof said positions; and means to vary the resistance of said biasingmeans.

References Cited in the file of this patent UNITED STATES PATENTS2,452,671 Merrill s Nov. 2, 1948 2,719,062 Arps Sept. 27, 1955 2,837,378Williams et ai. June 3, 1958 2,837,379 Selyem et al June 3, 19582,962,002 Hayner Nov. 29, 1960 2,964,023 Meulendyk Dec. 13, 1960

1. A TRACK LAYING VEHICLE COMPRISING: WHEELS; RESILIENT TIRES ON THEWHEELS; AT LEAST ONE FLEXIBLE BAND TRACK TIGHTLY ENGAGING AT LEAST TWOWHEELS; FLUID PRESSURE OPERATED MEANS TO MAINTAIN TENSION IN THE TRACK;A SOURCE OF FLUID UNDER PRESSURE; A CONDUIT HAVING A CONNECTION WITH THESOURCE; A SECOND CONDUIT FOR THE DISCHARGE OF SPENT FLUID; A THIRDCONDUIT CONNECTED WITH THE FLUID PRESSURE OPERATED MEANS; A FLUIDPRESSURE RESPONSIVE FLUID CONDUCTING ELEMENT HAVING PASSAGES AND ANOPERATING POSITION IN WHICH THE PASSAGES CONNECT THE FIRST AND THIRDCONDUITS AND A SECOND OPERATING POSITION IN WHICH THE PASSAGES CONNECTTHE FIRST AND THIRD CONDUITS AND A SECOND OPERATING POSITION IN WHICHTHE PASSAGES CONNECT THE SECOND AND THIRD CONDUITS; MEANS BIASING SAIDELEMENT AGAINST FLUID PRES-